Searching and resuming the visible child Tasks behind invisible one

The top-most Task was invisible because all activities in the Task
was finishing. This somehow prevents the activities of Tasks behind
from being resumed.

Bug: 260691453
Test: atest TaskTests
Test: Repro steps on the bug
Change-Id: I1fdda18a118915b4328d62e9d0984581fafa4f44
1 file changed